Antistatic polyester film and antistatic film laminate

ABSTRACT

The present invention provides an antistatic polyester film having an antistatic layer formed of an antistatic agent (A) composed mainly of a polymer having a recurring unit of a structure expressed by the following formula (I) on at least one surface of a polyester film ##STR1## wherein R 1  and R 2  are each H or CH 3 , R 3  is an alkylene group having a carbon number of 2 to 10, R 4  and R 5  are each a saturated hydrocarbon group having a carbon number of 1 to 5, R 6  is an alkylene group having a carbon number of 2 to 5, n is a number of 0 to 40, m is a number of 1 to 40, and Y -   is a halogen ion, a mono- or polyhalogenated alkyl ion, nitrate ion, sulfate ion, an alkylsulfate ion, sulfonate ion or an alkylsulfonate ion.

DETAILED DESCRIPTION OF THE INVENTION

1. Technical Field

This invention relates to an antistatic polyester film, moreparticularly to an antistatic polyester film having excellentantistaticity, back-transfer resistance, chipping resistance, blockingresistance and reclaimability and suitable for magnetic cards (forexample telephone card or prepaid card), electronic materials, graphicmaterials, graphic arts films, OHP films, magnetic recording materials(for example magnetic tapes such as audio tape or video tape or magneticdisks such as floppy disk), etc., especially for magnetic cards.

2. Background Art

Polyester films made of a polyester such as polyethylene terephthalateor polyethylene 2,6-naphthalate are widely in use as a film for magneticcard, general industrial materials such as a packaging material, aphotographic material or a graphic material and magnetic recordingmaterials such as a magnetic recording tape. However, these polyestershave defects of high surface resistivity to readily accumulate staticcharge by friction, etc. Accumulation of static charge on a polyesterfilm induces the deposition of dust on the film surface and causes theproblem of product deficiency. Further, a spark discharge may occurduring the production or the processing of the film to arise the problemof ignition hazard when an organic solvent is used in the aboveprocedures.

Various methods for forming an antistatic layer on the film surface havebeen proposed and put into practical use as a means for preventing theproblems caused by the static charge accumulation of these films. Theformation of an antistatic layer on a film surface is usually performedby coating the film surface with a coating liquid containing anantistatic agent.

Low-molecular weight compounds and high-polymer compounds are known asthe antistatic agents to be included in the antistatic coating film, andeach type of the antistatic agent has respective merits and demerits.Accordingly, the low-molecular antistatic agent and the high-polymerantistatic agent are properly used according to the use of the product.

Known antistatic agents and their characteristics are described below.

Surfactant-type anionic antistatic agents such as a long-chain alkylcompound having a sulfonic acid salt group (Japanese Patent TOKKAIHEI4-28728) are known as the low-molecular antistatic agent, and polymershaving ionized nitrogen element on the main chain (Japanese PatentsTOKKAIHEI 3-255139, 4-288217 and 6-172562) or a polystyrene modifiedwith a sulfonic acid salt (Japanese Patent TOKKAIHEI 5-320390) are knownas the high-polymer antistatic agent.

The use of a low-molecular antistatic agent may cause the migration of apart of the antistatic agent in the antistatic film through the coatingfilm layer and the accumulation of the agent to the interface betweenthe coating film and the base film and, for example in the case ofwinding the film in the form of a roll, produce a problem of thetransfer of the antistatic agent to the reverse face of the antistaticfilm (back transfer) and the deterioration of the antistatic effect withtime. As for the high-polymer antistatic agent, it is necessary to forma thick antistatic layer for getting sufficient antistatic effect tonecessitate a large amount of the antistatic agent and increase thecost.

Another problem is the thermal deterioration of the coating filmcomponent in the reclaimed material during a film-forming process togive a considerably colored film unsuitable for practical use in thecase of reclaiming a scrap film (for example, slit edge of the film inthe production of an antistatic film) and using as a reclaimed materialfor the production of a film.

Furthermore, these antistatic agents cause various problems such as thetendency of blocking (a phenomenon to cause the adhesion of films in ahardly peelable state in the case of stacking films over a long period)and the readily peelable antistatic layer.

DISCLOSURE OF INVENTION

The first object of the present invention is to solve the problems ofthe prior arts and provide an antistatic polyester film having excellentantistaticity, back-transfer resistance, reclaimability, chippingresistance and blocking resistance.

The second problem of the present invention is to provide an antistaticfilm laminate A resistant to the deposition of dust caused by the staticcharge of the film during the production of the film or film laminate,useful as a magnetic card and produced by laminating a magnetic layer onone surface of the above antistatic polyester film.

The third object of the present invention is to provide an antistaticfilm laminate B having excellent ink receptivity by applying anultraviolet curable ink layer to a face opposite to the magnetic layerface of the antistatic film laminate A.

BEST MODE FOR CARRYING OUT THE INVENTION

According to the investigation performed by the inventors of the presentinvention, the objects of the present invention can be achieved by anantistatic polyester film having an antistatic layer composed of anantistatic agent (A) composed mainly of a polymer having the recurringunit of the structure expressed by the following formula (I) on at leastone surface of a polyester film. ##STR2## In the formula (I), R¹ and R²are each H or CH₃, R³ is an alkylene group having a carbon number of 2to 10, R⁴ and R⁵ are each a saturated hydrocarbon group having a carbonnumber of 1 to 5, R⁶ is an alkylene group having a carbon number of 2 to5, n is a number of 0 to 40, m is a number of 1 to 40, and Y⁻ is ahalogen ion, a mono- or polyhalogenated alkyl ion, nitrate ion, sulfateion, an alkylsulfate ion, sulfonate ion or an alkylsulfonate ion.

<Polyester>

The polyester constituting the base film of the antistatic polyesterfilm of the present invention is a linear polyester composed of adicarboxylic acid component and a glycol component.

The dicarboxylic acid component is, for example, terephthalic acid,isophthalic acid, 2,6-naphthalenedicarboxylic acid,hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid, adipic acid,sebacic acid or dodecanedicarboxylic acid and, especially preferablyterephthalic acid or 2,6-naphthalenedicarboxylic acid.

The glycol component is, for example, ethylene glycol, diethyleneglycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentylglycol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol,polyethylene glycol or polytetramethylene glycol and especiallypreferably ethylene glycol.

Polyethylene terephthalate or polyethylene 2,6-naphthalate is preferableamong the above polyesters to give a film having excellent mechanicalproperties (e.g. Young's modulus) and thermal properties (e.g. thermaldimensional stability).

The above polyesters may be polyester copolymers copolymerized with theabove dicarboxylic acid component and/or glycol component as thirdcomponents or a polyester copolymers copolymerized with a small amountof a three or more functional polybasic carboxylic acid component and/orpolyol component in an amount to form an essentially linear polyester(for example 5 mol % or less).

The polyester of the present invention can be produced by a conventionalmethod and there is no restriction on the production method.

For example, in the case of polyethylene terephthalate, the polyestercan be produced preferably by esterifying terephthalic acid, ethyleneglycol and as necessary a copolymerizing component and subjecting theproduced reaction product to polycondensation reaction or by carryingout ester interchange reaction of dimethyl terephthalate with ethyleneglycol and, as necessary, a copolymerizing component and subjecting theproduced reaction product to polycondensation reaction.

The intrinsic viscosity of the polyester is preferably 0.45 or above toget a substrate film having desirable mechanical properties (especiallyrigidity).

The intrinsic viscosity of the polyester was measured in o-chlorophenolat 35° C.

The polyester may be incorporated with a lubricant consisting of organicor inorganic fine particles having an average particle diameter of about0.01 to 2.0 μm in an amount of for example 0.001 to 5 percent by weightto improve the slipperiness of the obtained antistatic film. Concreteexamples of preferable fine particles are silica, alumina, kaolin,calcium carbonate, calcium oxide, titanium oxide, graphite, carbonblack, zinc oxide, silicon carbide, tin oxide, crosslinked acrylic resinparticles, crosslinked polystyrene particles, melamine resin particlesand crosslinked silicone resin particles.

The polyester may be incorporated, in addition to the above additives,with colorants, known antistatic agents, antioxidants, organiclubricants (slip agent), catalysts, fluorescent brighteners,plasticizers, crosslinking agents, ultraviolet absorbers, other resins,etc.

<Base Film>

A transparent polyester film or a white polyester film can be used asthe base film of the antistatic film of the present invention accordingto the use of the antistatic film. The light transmittance of thetransparent polyester film is preferably not less than 60%, especiallynot less than 80% after drawing. The white polyester film is the abovepolyester compounded with 5 to 30% by weight of titanium oxide, bariumsulfate, silicon dioxide, etc., and has a light transmittance ofpreferably less than 60%, especially 30% or less in drawn state. Thewhite antistatic film produced by using a white polyester film as thebase film is especially preferable for a magnetic card, etc.

<Antistatic Agent (A)>

In the present invention, an antistatic layer containing an antistaticagent (A) composed mainly of a polymer having a recurring unit expressedby the following formula (I) is applied to at least one surface of apolyester film. ##STR3## In the formula (I), R¹ and R² are each H orCH₃, R³ is an alkylene group having a carbon number of 2 to 10, R⁴ andR⁵ are each a saturated hydrocarbon group having a carbon number of 1 to5, R⁶ is an alkylene group having a carbon number of 2 to 5, n is anumber of 0 to 40, m is a number of 1 to 40, and Y⁻ is a halogen ion, amono- or polyhalogenated alkyl ion, nitrate ion, sulfate ion, analkylsulfate ion, sulfonate ion or an alkylsulfonate ion.

A compound of the formula (I) wherein Y⁻ is an alkylsulfonate ionexpressed by R⁹ SO₃ ⁻ (R⁹ is a saturated hydrocarbon group having acarbon number of 1 to 5) and R⁶ is ethylene group is preferable amongthe above-mentioned antistatic agents (A) because of high adhesivity ofthe antistatic layer to the polyester film and heat-resistance of theantistatic layer and excellent antistaticity.

More preferable compound is the compound of the formula (I) wherein Y⁻is CH₃ SO₃ ⁻, C₂ H₅ SO₃ ⁻ or C₃ H₇ SO₃ ⁻, R⁶ is ethylene group and m is1 to 10.

Furthermore, the antistatic agent (A) of the formula (I) wherein R³ isethylene group is preferable when the number n is 1 to 40.

The antistatic agent (A) can be produced preferably e.g. by thefollowing method.

An acrylic acid ester monomer is polymerized by emulsion polymerizationto obtain a polyacrylic acid ester having a weight-average molecularweight of 2,000 to 100,000, the obtained polymer is amidated by reactingwith an N,N-dialkylaminoalkylamine (e.g. N,N-dimethylaminopropylamine orN,N-diethylaminopropylamine) and finally the product is subjected to aquaternary hydroxyalkylation reaction to introduce a quaternary cationpair.

The average molecular weight (number-average molecular weight) of theantistatic agent (A) is arbitrary, however, it is preferably 3,000 to300,000, especially 5,000 to 100,000. When the average molecular weightis less than 3,000, the back transfer resistance of the antistatic filmbecomes poor and when the molecular weight exceeds 300,000, theviscosity of the aqueous coating liquid becomes too high to enable theuniform application to the base film.

<Binder Resin (B)>

The antistatic layer of the present invention preferably contains abinder resin (B) to improve the adhesivity of the antistatic layer tothe polyester film. Examples of the binder resin (B) are polyester resin(B-1), acrylic resin (B-2) and acryl-modified polyester resin (B-3) andone or more resins selected from the examples are preferably used as thebinder resin. The use of the polyester resin (B-1) or the acrylic resin(B-2) is more preferable to improve the adhesivity of the antistaticlayer to the polyester film. The combined use of the polyester resin(B-1) with the acrylic resin (B-2) is especially preferable to attainhigh adhesivity and suppress the color development of a reclaimed filmin the case of reclaiming and reusing the waste antistatic film. Theamount of the polyester resin (B-1) is preferably larger than that ofthe acrylic resin (B-2) in the case of using the polyester resin (B-1)in combination with the acrylic resin (B-2).

<Polyester Resin (B-1)>

The polyester resin (B-1) is a linear polyester containing adicarboxylic acid component and a glycol component as constituentcomponents.

The preferable examples of the dicarboxylic acid component areterephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid,4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid,dodecanedicarboxylic acid and hexahydroterephthalic acid.

The preferable examples of the glycol component are ethylene glycol,diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol,neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol,triethylene glycol, an alkylene oxide adduct of bisphenol A, an alkyleneoxide adduct of hydrogenated bisphenol A, 1,4-cyclohexane-dimethanol,polyethylene glycol and polytetramethylene glycol.

The polyester resin (B-1) may be copolymerized, in addition to the abovecomponents, with a component having a sulfonic acid salt group to impartthe resin with hydrophilicity. The dispersibility in a water-basedcoating liquid can be improved by imparting the polyester resin (B-1)with hydrophilicity. Such component is, for example, 5-Nasulfoisophthalic acid or 5-K-sulfoisophthalic acid.

The polyester resin (B-1) may be copolymerized with a small amount of athree or more functional polyvalent compound in an amount within a rangeto get an essentially linear polyester resin (for example 5 mol % orless). Such three or more functional polyvalent compound is e.g.trimellitic acid, pyromellitic acid, dimethylolpropionic acid, glycerolor trimethylolpropane.

<Acrylic Resin (B-2)>

The acrylic resin (B-2) is a polymer or copolymer composed mainly ofacrylic monomers exemplified by ethyl acrylate, methyl acrylate, acrylicacid, butyl acrylate, sodium acrylate, ammonium acrylate, ethylmethacrylate, methyl methacrylate, methacrylic acid, butyl methacrylate,glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide,methacrylamide, N-methoxymethyl acrylamide or N-methylol acrylamide. Itmay be a copolymer copolymerized, in addition to the above monomers,with copolymer components such as styrene, α-methylstyrene, sodiumstyrenesulfonate, vinyl chloride, vinylidene chloride, vinyl acetate,vinyl ether, sodium vinylsulfonate, sodium methacrylate, butadiene orisoprene.

The second order transition point of the acrylic resin (B-2) forming theantistatic layer is preferably 20 to 100° C. An acrylic resin (B-2)having a second order transition point of lower than 20° C. may havepoor blocking resistance, and the chipping resistance may bedeteriorated when the second order transition point exceeds 100° C.

The blocking resistance is the resistance to develop the mutual adhesion(blocking) of films in the case of storing a continuous film in a formwound in a roll, and the chipping resistance is the resistance of theseparation (chipping) of the antistatic layer from the base polyesterfilm when the antistatic film is subjected to friction or pressing forcewith a roll in processing.

<Acryl-modified polyester Resin (B-3)>

The aforementioned acryl-modified polyester resin (B-3) is a graftcopolymer produced by the copolymerization of the monomer of the abovepolyester resin (B-1) with acrylic monomers exemplified by ethylacrylate, methyl acrylate, acrylic acid, butyl acrylate, sodiumacrylate, ammonium acrylate, ethyl methacrylate, methyl methacrylate,methacrylic acid, butyl methacrylate, glycidyl methacrylate,2-hydroxyethyl acrylate, acrylamide, methacrylamide,N-methoxymethylacrylamide and N-methylol acrylamide and may containother monomers such as styrene, α-methylstyrene, sodiumstyrenesulfonate, vinyl chloride, vinylidene chloride, vinyl acetate,vinyl ether, sodium vinylsulfonate and sodium methacrylate in additionto the above monomers as copolymerizing components.

The antistatic layer of the present invention may be incorporated with abinder resin other than the aforementioned resins to control theadhesivity between the coating film and the polyester film. Examples ofthe binder resins are polyurethane resin, epoxy resin, vinyl resin,polyether resin and water-soluble resin.

<Crosslinking Agent (C)>

The antistatic layer of the present invention is preferably incorporatedwith a crosslinking agent (C) composed mainly of a polymer having therecurring unit of the structure expressed by the following formula (II)in order to improve the solvent resistance of the coating film or theblocking resistance of the antistatic film. ##STR4##

In the formula (II), R⁷ and R⁸ are each H or CH₃.

The molecular weight of the polymer having the recurring unit of thestructure expressed by the formula (II) is preferably between 500 and5,000. The solvent resistance of the antistatic layer or the blockingresistance of the film may be lowered when the molecular weight issmaller than 500, and a polymer having a molecular weight exceeding5,000 may cause the failure in getting a uniform antistatic layer.

Among the polymers having the recurring unit of the structure expressedby the formula (II), especially preferable polymers are those containingthe recurring unit of the formula (II) wherein groups R⁷ and R⁸ are Hand CH₃, respectively and having a molecular weight of about 2,000.

<Surfactant (D)>

The antistatic layer of the present invention is preferably formed bycoating a base film with a coating liquid, especially a water-basedcoating liquid, containing the aforementioned antistatic agent (A) andoptionally the binder resin (B) or the crosslinking agent (C).

The coating liquid is preferably incorporated with a surfactant forimproving the stability of the coating liquid, especially thewater-based coating liquid, and improving the wettability of the liquidin the case of applying the coating liquid to the base film.

The surfactant (D) is, for example, a nonionic surfactant such as analkylene oxide homopolymer, an alkylene oxide copolymer, an additionproduct of an aliphatic alcohol and an alkylene oxide, an additionpolymer of a phenolic compound substituted with a long-chain aliphaticgroup and an alkylene oxide, a polyhydric alcohol fatty acid ester and along-chain aliphatic amide alcohol, or a cationic or anionic surfactantsuch as a compound having quaternary ammonium salt, a compound havingalkylpyridinium salt or a compound having sulfonic acid group. Among theabove compounds, nonionic surfactants, especially polyoxyethylenenonylphenyl ether is most preferable.

<Composition of Coating Liquid>

The antistatic layer of the present invention is preferably formed bycoating a base film with a coating liquid, especially a water-basedcoating liquid, containing the aforementioned antistatic agent (A) andoptionally the binder resin (B), the crosslinking agent (C) and/or thesurfactant (D).

The coating liquid preferably has a solid composition consisting of 5 to100% by weight of the antistatic agent (A) and 0 to 95% by weight of thebinder resin (B). The antistaticity of the antistatic polyester filmfrequently becomes insufficient when the content of the antistatic agent(A) is less than 5% by weight.

The following compositions (α), (β) and (γ) are preferable examples ofthe solid composition of the coating liquid.

(α): 1. 5 to 99% by weight of an antistatic agent (A) (a polymer havingthe recurring unit of the structure expressed by the aforementionedformula (I))

2. 0 to 95% by weight of a binder resin (B)

3. 1 to 15% by weight of a crosslinking agent (C) (a polymer having therecurring unit of the structure shown by the aforementioned formula(II)),

(β): 1. 10 to 80% by weight of the antistatic agent (A) (a polymerhaving the recurring unit of the structure expressed by theaforementioned formula (I) and having a weight-average molecular weightof 3,000 to 300,000 (in the formula (I), R¹ and R² are each hydrogenatom or methyl group, R³ is an alkylene group having a carbon number of2 to 10, R⁴ and R⁵ are each a saturated hydrocarbon group having acarbon number of 1 to 5, R⁶ is ethylene group, and Y⁻ is analkylsulfonate ion expressed by R⁹ SO₃ ⁻ (wherein R⁹ is a saturatedhydrocarbon group having a carbon number of 1 to 5)),

2. 20 to 80% by weight of a binder resin (B) (an acrylic resin having asecond order transitino point of 20 to 100° C.),

3. 0 to 25% by weight of a surfactant (D) and

(γ) 1. 10 to 80% by weight of a surfactant (A) (a polymer having therecurring unit of the structure expressed by the formula (I) and havinga weight-average molecular weight of 3,000 to 300,000 (in the formula(I), R¹ and R² are each hydrogen atom or methyl group, R³ and R⁶ areeach an ethylene group, R⁴ and R⁵ are each a saturated hydrocarbon grouphaving a carbon number of 1 to 5, and Y⁻ is an alkylsulfonate ionexpressed by R⁹ SO₃ ⁻ (wherein R⁹ is a saturated hydrocarbon grouphaving a carbon number of 1 to 5)),

2. 19 to 80% by weight of a binder resin (B) (an acrylic resin having asecond order transition point of 20 to 100° C.)

3. 1 to 10% by weight of a crosslinking agent (C) (a polymer having therecurring unit of the structure expressed by the formula (II)),

4. 0 to 25% by weight of a surfactant (D).

Among the above preferable examples of the solid composition of thecoating liquid, especially preferable compositions are the compositions(β) and (γ) giving an antistatic layer having a surface energy of 37 to73 dyne/cm and a water contact angle of 40 to 110 degrees to improve theadhesivity of the antistatic layer to the base film and get anantistatic film having excellent blocking resistance, heat-resistanceand antistaticity at a low humidity in the case of using the antistaticpolyester film e.g. as a magnetic card.

The surface energy of the antistatic layer is measured in conformitywith JIS K6768 by measuring a wettability index with a wettability indexliquid and using the index as the surface energy.

The contact angle with water is measured by setting a specimen film on acontact angle measuring instrument (product of Elmer Co.) directing themeasuring face upward, dropping a water drop at 23° C. and measuring thecontact angle after 1 minute.

An antistatic layer having a surface energy of 37 to 73 dyne/cm and awater contact angle of 40 to 110 degrees is especially preferablebecause of excellent antistaticity and adhesivity between the antistaticfilm and an ultraviolet-curable ink. The antistatic coating film givingan antistatic layer having the surface energy and the water contactangle falling within the above ranges can be produced by adding anantistatic agent (A), a binder resin (B), a crosslinking agent (C) and asurfactant (D) to obtain a solid composition falling within theaforementioned composition ranges (α), (β) or (γ).

For example, since an antistatic agent (A) has an action to increase thesurface energy of an antistatic layer, the energy is adjusted within theabove range by compounding a binder resin (B) and, as necessary, addinga surfactant (D). Since an antistatic agent (A) also acts to decreasethe water contact angle of the antistatic layer, the angle is adjustedwithin the above range by compounding a binder resin and, as necessary,adding a surfactant (D).

Further, the coating liquid may be compounded with a lubricant in thepresent invention to improve the surface slipperiness of the antistaticlayer and the anbiblocking property of the antistatic film.

The lubricant is fine particles of e.g. a polystyrene, an acrylic resin,a melamine resin, a silicone resin, a fluororesin, a urea resin, abenzoguanamine resin, a polyamide resin or a polyester resin. Theseresins may be thermoplastic resin or thermosetting resin provided thatthe resin is present in the antistatic coating film in the form of fineparticles.

The coating liquid may be compounded with additional ingredients such asan antistatic agent other than the aforementioned antistatic agent (A),a crosslinking agent other than the aforementioned crosslinking agent(C), a surfactant other than the aforementioned surfactant (D), anantioxidant, a colorant, a pigment, a fluorescent brightener, aplasticizer, a wax, and an ultraviolet absorber.

The solid concentration of the coating liquid is preferably 1 to 30% byweight, especially 2 to 20% by weight. A coating liquid having a solidconcentration falling within the above range has a viscosity suitablefor application. The coating liquid to be used in the present inventionis preferably a water-based coating liquid, which is usable in anarbitrary form such as an aqueous solution, an aqueous dispersion or anemulsion. The water-based coating liquid may contain a small amount ofan organic solvent.

<Production of Antistatic Film>

The antistatic polyester film of the present invention can be producedby conventional processes. For example, it can be produced by meltingthe aforementioned polyester, extruding the molten polyester on acooling drum in the form of a sheet to form an undrawn film and drawingthe undrawn film by a successive biaxial drawing method comprising thedrawing of the undrawn film in longitudinal direction and then intransversal direction or by a simultaneous biaxial drawing methodcomprising the drawing of the undrawn film in the longitudinal directionand the transversal direction at the same time. The biaxially drawn filmmay be drawn further in longitudinal direction and/or transversaldirection. The drawing is preferably carried out at a temperature higherthan the second order transition point (Tg) of the polyester at a drawratio of 2.5 or more, especially 3 or more in each direction. The arealdraw ratio is preferably 8 or more, especially 9 or more. The upperlimit of the areal draw ratio depends upon the use of the film and ispreferably 35, especially 30. The drawn film is preferably heat-treatedafter drawing to complete the orientation and crystallization of thefilm.

In the present invention, it is preferable that at least one surface ofthe polyester film is coated with the aforementioned coating liquid, thecoating liquid is dried by heating and the film is drawn to form anantistatic layer. The coating with the coating liquid can be carried outby an arbitrary conventional coating process.

The coating process is, for example, gravure coating, reverse rollcoating, die coating, kiss coating, reverse kiss coating, offset gravurecoating, Meyer bar coating, roll brush coating, spray coating, air knifecoating, impregnation or curtain coating or their combination.

The application amount of the coating liquid is preferably 1 to 20 g,especially 2 to 12 g per 1 m² of the running film. The drying is easyand the coating uniformity is improved when the application amount iswithin the above range.

The polyester film to be coated with the coating liquid in the presentinvention is a drawable polyester film such as

(a) an undrawn film produced by forming a film from molten polyester asit is,

(b) a uniaxially drawn film produced by drawing an undrawn film eitherin longitudinal direction (direction of length) or in transversaldirection (direction of width),

(c) a (further drawable) biaxially drawn film produced from a uniaxiallydrawn film drawn in longitudinal direction or transversal direction bysuccessively drawing the uniaxially drawn film in transversal directionor longitudinal direction, or

(d) a (further drawable) biaxially drawn film produced by thesimultaneous drawing of an undrawn film in longitudinal and transversaldirectoins.

The coating liquid is preferably applied to the uniaxially drawn film(b), especially a film uniaxially drawn in longitudinal direction amongthe above drawable polyester films to ensure the firm bonding of theantistatic coating film and improve the production efficiency of theantistatic polyester film.

The coating liquid applied to the base film is dried preferably at 80 to160° C. in the present invention to effect quick drying of the coatingliquid. The heating in the drawing of the polyester film may be usedalso for the drying of the coating liquid. The heat-treatmenttemperature of the polyester film is 180 to 250° C.

The thickness of the antistatic layer applied by the aforementionedmethod is preferably 0.005 to 3 μm, especially 0.01 to 1 μm. A coatingfilm thinner than 0.005 μm may cause insufficient antistaticity andthicker than 3 μm may form an easily peelable coating film.

<Film Laminate>

The antistatic polyester film of the present invention is useful formagnetic card and a white antistatic polyester film produced by using awhite polyester film as the base film is especially preferable formagnetic card.

The magnetic card is a card manufactured by applying a magneticrecording layer (magnetic layer) to a surface of e.g. an antistatic filmand a printed layer on the other surface with a UV ink, etc.

The outlines of the constitution of such magnetic card are explained asfollows.

First, an antistatic film laminate A is produced by coating a surface ofan antistatic polyester film of the present invention with a magneticcoating composed of e.g. magnetic iron oxide, a modified vinyl chlorideresin, a polyurethane resin, a polyisocyanate, a dispersing agent, etc.,and drying the coating layer to form a magnetic recording layer. Themagnetic recording layer of the antistatic film laminate A is preferablyfurther covered with a protection layer.

Subsequently, the surface of the antistatic film laminate A opposite tothe surface laminated with the magnetic recording layer, e.g. thesurface of the base film coated with the antistatic coating film isprinted with an ultraviolet ink produced by compounding aphoto-sensitizer, a colorant, etc., e.g. to a polyurethane oligomerhaving acrylic group on the terminal or a vinyl polymer having acrylicgroup on the terminal, and the printed ink is cured by ultravioletirradiation to form an antistatic film laminate B, i.e. a magnetic card.

The thickness of the antistatic polyester film to be used in themagnetic card is e.g. 50 to 300 μm, especially 1.50 to 250 μm to obtaina magnetic card having desirable rigidity.

A transparent antistatic film produced by using a transparent polyesterfilm as the base can be used preferably for a magnetic recordingmaterial or an electronic material such as magnetic tape and magneticdisk, a graphic film, a graphic arts film, an OHP film, etc. Thethickness of the antistatic polyester film depends upon its use and ispreferably e.g. 5 to 160 μm, especially 5 to 100 μm.

EXAMPLES

The present invention is described in detail by the following Examples.The characteristic values were measured and evaluated by the followingmethods. The average molecular weight cited in the Examples and theComparative Examples means number-average molecular weight.

1. Surface Resistivity

(1) Measurement 1 (Surface resistivity 1)

The surface resistivity of the antistatic layer of an antistaticpolyester film was measured by a vibrating reed electrometer (product ofTakeda Riken Co., Type TR-84M) after conditioning the specimen film at21° C. and 52% RH for 19 hours. The applied potential was 100V.

(2) Measurement 2 (Surface resistivity 2)

The surface resistivity of the antistatic layer of an antistaticpolyester film was measured by a vibrating reed electrometer (product ofTakeda Riken Co., Type TR-84M) after conditioning the specimen film at23° C. and 60% RH for 19 hours. The applied potential was 500V.

2. Contact Angle with Water

A specimen film was set on a contact angle measuring instrument (productof Elmer Co.) directing the measuring face upward, a waterdrop wasdropped on the surface at 23° C. and the contact angle was measuredafter 1 minute.

3. Back-transfer Resistance

The antistatic layer of an antistatic polyester film was brought intocontact with the non-antistatic surface, the laminate was maintainedunder a condition of 50° C.×70% RH for 8 hours or more, the watercontact angle (θ: an alternative characteristic of the back-transferresistance) of the non-antistatic surface was measured by the method ofthe preceding item 2, and the back-transfer resistance was evaluatedaccording to the following criterion/

    ______________________________________                                        A:             θ ≧ 55°                                                              Good back-transfer resistance                       B:    55° >                                                                           θ ≧ 48°                                                              Fair back-transfer resistance                       C:    48° >                                                                           θ    Poor back-transfer resistance                       ______________________________________                                    

The water contact angle of a film absolutely free from back-transfer is60 to 75 degrees, that of a film having good back-transfer resistance is55 degrees or more and the contact angle of a film exhibiting remarkableback-transfer (poor back-transfer resistance) is less than 48 degrees.

4. Discoloration Tendency of Film (reclaimability)

A film free from antistatic layer was crushed, melted with an extruderat about 300° C. and pelletized. The produced pellets were melted andformed in the form of a film to obtain a blank film. The discolorationtendency of the film was used as the blank. A specimen film having anantistatic layer was crushed, melted with an extruder at about 300° C.and pelletized. The produced pellets were melted and formed in the formof a film to obtain a reclaimed film. The discoloration degree of thefilm was compared with that of the blank film and evaluated by thefollowing criterion.

Rank A: The discoloration degree is comparable to the blank film.

Rank B: The film is faintly tinted.

Rank C: The film is remarkably tinted and unsuitable for practical use.

5. Saturated Electrostatic Voltage

A voltage of 10 KV was applied to the antistatic layer of a specimenfilm conditioned under a condition of 22° C. ×44% RH for 10 hours, theelectrostatic voltage of the surface of the antistatic layer wasmeasured with time until the change in the electrostatic voltage becameunnoticeable, and the voltage was used as the saturated electrostaticvoltage. The film was evaluated from the value of the saturatedelectrostatic voltage by the following criterion.

Rank A: 1 KV≧saturated electrostatic voltage (no problem for practicaluse)

Rank B: 2 KV≧saturated electrostatic voltage>1 KV (causes somedifficulty in practical use)

Rank C: saturated electrostatic voltage>2 KV (difficult for practicaluse)

6. Ink Receptivity

An ultraviolet ink (a mixture of a bisacryl polyurethane oligomer, aphotopolymerization initiator, a photosensitizer and a red colorant) wasapplied to the surface of the antistatic layer of a specimen film at athickness of 8 μm, the coating layer was cured by ultravioletirradiation, a cellophane tape was pasted to the surface of the curedultraviolet ink layer, the cellophane tape is peeled off, the peelingstate between the layers was observed, and the ink receptivity wasevaluated according to the following criterion.

Rank A: Peeled between the cellophane tape and the ink layer (good inkreceptivity)

Rank B: Peeled between the cellophane tape and the ink layeraccompanying partial cohesive failure (fair ink receptivity)

Rank C: Peeled between the antistatic layer and the ink layer (poor inkreceptivity)

7. Heat-resistance

Twenty two (12) grams of a specimen film having an antistatic layer wasmelted by heating at 300° C. in nitrogen atmosphere, maintained in thestate for 15 minutes and quenched to form a disk-shaped specimen and thediscoloration degree of the specimen was observed. Separately, adisk-shaped specimen was prepared from a film free from antistatic layerunder the same conditions and used as a blank. The discoloration degreeof the specimen was compared with that of the blank and theheat-resistance was evaluated by the following criterion.

Rank A: Colored to an extremely pale yellow color comparable to thecolor of the blank (good heat-resistance)

Rank B: Colored to pale yellow color slightly denser than the blank(fair heat-resistance)

Rank C: Colored to yellow color denser than the blank (poorheat-resistance)

8. Blocking resistance

(1) Measurement 1 (Blocking resistance 1)

The antistatic layer of a specimen film slit to 10 mm width was broughtinto contact with the non-antistatic surface of the film, the laminatewas maintained in the state under a load of 50 kg/cm² at 50° C. for 10hours, the peeling force between the antistatic layer and thenon-antistatic layer was measured, and the blocking resistance wasevaluated according to the following criterion.

Rank A: Peeling force≦7 g (good blocking resistance)

Rank B: 7 g<peeling force≦10 g (rather poor blocking resistance)

Rank C: 10 g≦peeling force (poor blocking resistance)

(2) Measurement 2 (Blocking resistance 2)

The antistatic layer of a specimen film slit to 50 mm width was broughtinto contact with the non-antistatic surface of the film, the laminatewas maintained in the state under a load of 50 kg/cm² at 60° C. and 80%RH for 17 hours, the peeling force between the antistatic layer and thenon-antistatic layer was measured, and the blocking resistance wasevaluated according to the following criterion.

Rank A: Peeling force≦10 g (good blocking resistance)

Rank B: 10 g<peeling force≦30 g (rather poor blocking resistance)

Rank C: 30 g≦peeling force (poor blocking resistance)

9. Chipping Resistance

The antistatic layer of a specimen film slit to 20 mm width was broughtinto contact with a cylindrical stationary bar made of stainless steeland having a diameter of 10 mm, the specimen film was transported over alength of 80 meters under a load of 200 g, the white powder generatedfrom the antistatic layer and deposited on the bar was observed, and thechipping resistance was evaluated by the following criterion.

Rank A: No white powder on the bar (good chipping resistance)

Rank B: Some white powder observable on the bar (rather poor chippingresistance)

Rank C: Large amount of white powder deposited on the bar (poor chippingresistance)

10. Surface Energy

The wettability index was measured in conformity with JIS K6768 using awettability index liquid and the measured value was used as the surfaceenergy.

Example 1

A polyethylene terephthalate having an intrinsic viscosity of 0.63(measured in o-chlorophenol at 35° C.) was melted, extruded on a coolingdrum in the form of a sheet and drawn 3.6 times in longitudinaldirection at 92° C. to obtain a uniaxially draw film.

A surface of the uniaxially drawn film was coated with a water-basedcoating liquid having the following solid composition and aconcentration of 5% by weight using a gravure coater. The coated filmwas dried at 98° C., drawn 3.8 times in transversal direction at 105° C.and heat-treated to obtain a film having a thickness of 75 μm and coatedwith an antistatic layer. The thickness of the antistatic layer of thefilm was 0.34 μm and the light transmittance of the film was 84%. Thecharacteristics of the film were shown in the Table 1.

<Solid composition of the water-based coating liquid>

(1) 30% by weight of an antistatic agent (A): a polymer (a-1, averagemolecular weight: 7,000) having a recurring unit of the structure shownby the formula (I-1) to be described later,

(2) 60% by weight of a binder resin: a polyester copolymer (b-1, averagemolecular weight: 19,700) containing dicarboxylic acid componentsconsisting of terephthalic acid (54 mol %) and isophthalic acid (46 mol%) and glycol components consisting of ethylene glycol (42 mol %),diethylene glycol (12 mol %), neopentyl glycol (41 mol %) andpolyethylene glycol (5 mol %),

(3) 10% by weight of a surfactant (D): a polyoxyethylene nonylphenylether (the number of polyoxyethylene recurring units: 9).

Comparative Example 1

A film was prepared by a method similar to the Example 1 except for theomission of the application of the water-based coating liquid. Thecharacteristics of the produced film are shown in the Table 1.

Examples 2 to 8 and Comparative Examples 2 to 4

Films were prepared by the method similar to the Example 1 except forthe variation of the composition of the coating liquid and the thicknessof the coating layer to the values shown in the Table 1. Thecharacteristics of these films are shown in the Table 1.

Example 9

A film having a light transmittance of 2% was prepared by a methodsimilar to the Example 1 except for the use of a polyethyleneterephthalate having an intrinsic viscosity of 0.65 and containing 12%by weight of titanium dioxide, the film thickness of 150 μm and thecomposition of the coating liquid and the thickness of the coating layervaried to those described in the Table 1. The characteristics of thefilm are shown in the Table 1.

Examples 10 and 11

A film was prepared by the method similar to the Example 1 except forthe variation of the composition of the coating liquid and the thicknessof the coating layer to the values shown in the Table 1. Thecharacteristics of the film are shown in the Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Antistatic Layer         Characteristics of antistatic film                   Solid composition of coating liquid                                                                Thick-                                                                            Surface                                                                            Back     saturated                              (wt %)               ness of                                                                           resist-                                                                            transfer                                                                          Discolor-                                                                          static                                       Antistatic                                                                         Binder    coating                                                                           ivity                                                                              resis-                                                                            ation of                                                                           voltage                                      agent                                                                              resin                                                                              Surfactant                                                                         film (μ)                                                                       (Ω/□)                                                             tance                                                                             film (KV)                                   __________________________________________________________________________    Example 1                                                                           (a-1) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              1 × 10.sup.10                                                                A   A    0.1 A                                  Example 2                                                                           (a-1) 20%                                                                          (b-1) 70%                                                                          (d-1) 10%                                                                          0.15                                                                              2 × 10.sup.10                                                                A   A    0.2 A                                  Example 3                                                                           (a-2) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              5 × 10.sup.10                                                                A   A    0.2 A                                  Example 4                                                                           (a-3) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              5 × 10.sup.9                                                                 A   A    0.1 A                                  Example 5                                                                           (a-4) 40%                                                                          (b-1) 50%                                                                          (d-1) 10%                                                                          0.15                                                                              2 × 10.sup.10                                                                A   A    0.2 A                                  Example 6                                                                           (a-1) 30%                                                                          (b-2) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              8 × 10.sup.9                                                                 A   A    0.1 A                                  Example 7                                                                           (a-1) 30%                                                                          (b-3) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              1 × 10.sup.10                                                                A   A    0.1 A                                  Example 8                                                                           (a-1) 30%                                                                          (b-4) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              9 × 10.sup.9                                                                 A   A    0.1 A                                  Example 9                                                                           (a-1) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              1 × 10.sup.10                                                                A   A    0.1 A                                  Example 10                                                                          (a-1) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.30                                                                              1 × 10.sup.9                                                                 A   B    0.0 A                                  Example 11                                                                          (a-1) 60%                                                                          (b-1) 30%                                                                          (d-1) 10%                                                                          0.05                                                                              5 × 10.sup.10                                                                A   A    0.2 A                                  Comparative                                                                         --   --   --   --  10.sup.10 <                                                                        A   A    ∞ C                              Example 1                                                                     Comparative                                                                         (a-5) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              2 × 10.sup.14                                                                A   A    1.5 A                                  Example 2                                                                     Comparative                                                                         (a-6) 30%                                                                          (b-1) 60%                                                                          (d-1) 10%                                                                          0.10                                                                              1 × 10.sup.11                                                                C   A    0.3 A                                  Example 3                                                                     Comparative                                                                         --   (b-1) 90%                                                                          (d-1) 10%                                                                          0.10                                                                              10.sup.10 <                                                                        A   A    ∞ C                              Example 4                                                                     __________________________________________________________________________                     Characteristics of antistatic film                                            Ink Heat-                                                                            Blocking                                                                           Chipping                                                                           Surface                                                                            Contact                                                 recep-                                                                            resis-                                                                           resis-tance                                                                        resis-                                                                             energy                                                                             angle (*)                                               tivity                                                                            tance                                                                            1    tance                                                                              (dyne/cm)                                                                          (degree)                               __________________________________________________________________________               Example 1                                                                           A   A  A    A    60   60                                                Example 2                                                                           A   A  A    A    52   65                                                Example 3                                                                           A   A  A    A    58   62                                                Example 4                                                                           A   A  A    A    65   53                                                Example 5                                                                           A   A  A    A    53   66                                                Example 6                                                                           A   A  A    A    50   69                                                Example 7                                                                           A   A  A    A    55   63                                                Example 8                                                                           A   A  A    A    54   63                                                Example 9                                                                           A   A  A    A    64   52                                                Example 10                                                                          A   A  A    A    70   45                                                Example 11                                                                          A   A  B    A    68   48                                                Comparative                                                                         C   A  A    A    60   59                                                Example 1                                                                     Comparative                                                                         A   A  A    C    68   46                                                Example 2                                                                     Comparative                                                                         B   B  B    C    70   43                                                Example 3                                                                     Comparative                                                                         A   A  A    A    49   70                                                Example 4                                                          __________________________________________________________________________     (*) Contact angle of antistatic layer surface with water                 

Examples 12 to 19 and Comparative Examples 5 to 7

A polyethylene terephthalate (containing 10% by weight of titaniumoxide) having an intrinsic viscosity of 0.65 (measured in o-chlorophenolat 35° C.) was melted, extruded on a cooling drum in the form of a sheetand drawn 3.6 times in longitudinal direction at 92° C. to obtain auniaxially draw film.

A surface of the uniaxially drawn film was coated with a water-basedcoating liquid having a solid composition shown in the Table 2 and aconcentration of 10% by weight using a gravure coater at a rate of 4g/m². The coated film was dried at 98° C., drawn 3.6 times intransversal direction at 105° C. and heat-treated at 230° C. to obtain afilm having a thickness of 100 μm and having an antistatic layer. Thecharacteristics of the film are shown in the Table 2.

In the Example 18, a film was prepared by a method same as the Example14 except for the use of polyethylene naphthalate in place ofpolyethylene terephthalate.

In the Comparative Example 7, a film was prepared by the method same asthe Example 12 except for the omission of the coating with thewater-based coating liquid.

                                      TABLE 2                                     __________________________________________________________________________    Antistatic Layer               Characteristics of antistatic film             Solid composition of coating liquid (wt %)                                                                   Surface                                                                            Back                   Contact                                 Cross-    resist-                                                                            transfer                                                                          Discolor-                                                                          Ink Blocking  angle              Antistatic           linking                                                                            Surfac-                                                                            ivity                                                                              resis-                                                                            ation of                                                                           recep-                                                                            resistance                                                                         Chipping                                                                           (*)                agent      Binder resin                                                                            agent                                                                              tant (Ω/□)                                                             tance                                                                             film tivity                                                                            2    resistance                                                                         (degree)           __________________________________________________________________________    Example 12                                                                          (a-7) 20%                                                                          (b-5) 70% (c-1) 5%                                                                           (d-1) 5%                                                                           5 × 10.sup.11                                                                A   A    A   A    A    65                 Example 13                                                                          (a-7) 20%                                                                          (b-6) 70% (c-1) 5%                                                                           (d-1) 5%                                                                           3 × 10.sup.11                                                                A   A    A   A    A    64                 Example 14                                                                          (a-7) 30%                                                                          (b-5) 30%                                                                          (b-6) 30%                                                                          (c-1) 5%                                                                           (d-1) 5%                                                                           4 × 10.sup.11                                                                A   A    A   A    A    65                 Example 15                                                                          (a-8) 30%                                                                          (b-5) 30%                                                                          (b-6) 30%                                                                          (c-1) 5%                                                                           (d-1) 5%                                                                           1 × 10.sup.11                                                                A   A    A   A    A    66                 Example 16                                                                          (a-7) 7%                                                                           (b-5) 42%                                                                          (b-6) 41%                                                                          (c-1) 5%                                                                           (d-1) 5%                                                                           2 × 10.sup.12                                                                A   A    A   A    A    62                 Example 17                                                                          (a-7) 48%                                                                          (b-5) 21%                                                                          (b-6) 21%                                                                          (c-1) 5%                                                                           (d-1) 5%                                                                           9 × 10.sup.9                                                                 A   A    A   B    A    67                 Example 18                                                                          (a-7) 30%                                                                          (b-5) 30%                                                                          (b-6) 30%                                                                          (c-1) 5%                                                                           (d-1) 5%                                                                           2 × 10.sup.11                                                                A   A    A   A    A    65                 Example 19                                                                          (a-7) 20%                                                                          (b-5) 65% (c-1) 10%                                                                          (d-1) 5%                                                                           2 × 10.sup.11                                                                A   A    A   A    A    65                 Comparative                                                                         (a-5) 25%                                                                          (b-5) 65% (c-1) 5%                                                                           (d-1) 5%                                                                           10.sup.16 <                                                                        A   A    A   A    C    42                 Example 5                                                                     Comparative                                                                         (a-6) 25%                                                                          (b-5) 65% (c-1) 5%                                                                           (d-1) 5%                                                                           1 × 10.sup.12                                                                C   A    C   C    B    45                 Example 6                                                                     Comparative                                                                         --   --   --   --   --   10.sup.16 <                                                                        A   A    C   A    A    65                 Example 7                                                                     __________________________________________________________________________     (*) Contact angle of antistatic layer surface with water                 

In the solid composition of the coating liquid in the Table 1 and theTable 2, the terms (a-1), (a-2), (a-3), (a-4), (a-5), (a-6), (a-7) and(a-8) of the antistatic agent, (b-1), (b-2), (b-3), (b-4), (b-5) and(b-6) of the binder resin, (c-1) of the crosslinking agent and (d-1) ofthe surfactant are the following copolymers, compounds or mixtures.

(a-1) An antistatic agent (average molecular weight: 7,000) having therecurring unit of the structure expressed by the following formula (I-1)##STR5## (a-2) An antistatic agent (average molecular weight: 6,500)having the recurring unit of the structure expressed by the followingformula (I-2) ##STR6## (a-3) An antistatic agent (average molecularweight: 9,000) having the recurring unit of the structure expressed bythe following formula (I-3) ##STR7## (a-4) A copolymer (averagemolecular weight: 7,500) composed of 60 mol % of the unit componentexpressed by the above formula (I-1), 10 mol % of ethyl acrylate and 30mol % of methyl methacrylate

(a-5) A sodium polystyrenesulfonate (sulfonation degree: 98%) (averagemolecular weight: 20,000)

(a-6) A mixture consisting of 40% by weight of sodiumdodecylbenzenesulfonate and 60% by weight of sodium octylsulfate.

(a-7) An antistatic agent (average molecular weight: 15,000) consistingof a polymer having the recurring unit of the structure expressed by thefollowing formula (I-4) ##STR8## (a-8) An antistatic agent (averagemolecular weight: 25,000) consisting of a polymer having the recurringunit of the structure expressed by the following formula (I-5) ##STR9##(b-1) A copolymer (average molecular weight: 19,700) containingdicarboxylic acid components consisting of terephthalic acid (54 mol %)and isophthalic acid (46 mol %) and glycol components consisting ofethylene glycol (42 mol %), diethylene glycol (12 mol %), neopentylglycol (41 mol %) and polyethylene glycol (5 mol %)

(b-2) An acrylic copolymer (average molecular weight: 45,500) composedof methyl methacrylate (51 mol %), ethyl acrylate (39 mol %),hydroxyethyl acrylate (4 mol %) and N-methylol acrylamide (6 mol %)

(b-3) A mixture of 61% by weight of the polyester copolymer (b-1) and39% by weight of an acrylic copolymer consisting of 16 mol % of ethylacrylate component, 4 mol % of potassium acrylate component, 53 mol % ofmethyl methacrylate component, 12 mol % of glycidyl methacrylatecomponent, 7 mol % of 2-hydroxyethyl acrylate component and 8 mol % ofN-methoxymethyl acrylamide component.

(b-4) An acryl-modified polyester copolymer (average molecular weight:41,500) produced by the graft-polymerization of 42% by weight ofcomponents consisting of methyl acrylate (19 mol %), ammonium acrylate(8 mol %), ethyl methacrylate (62 mol %) and glycidyl methacrylate (11mol %) to 58% by weight of the polyester copolymer (b-1).

(b-5) A copolymer (glass transition point: 80° C., average molecularweight: 21,500) of dicarboxylic acid components consisting ofterephthalic acid (22 mol %), isophthalic acid (1 mol %),2,6-naphthalenedicarboxylic acid (65 mol %) and4,4'-diphenyldicarboxylic acid (12 mol %) and glycol componentsconsisting of ethylene glycol (75 mol %), 1,4-cyclohexanedimethanol (10mol %) and propylene oxide adduct of bisphenol A (15 mol %).

(b-6) An acrylic copolymer (average molecular weight: 258,000) of methylmethacrylate (30 mol %), ethyl acrylate (55 mol %), acrylonitrile (10mol %) and N-methylol methacrylamide (5 mol %).

(c-1) A crosslinking agent consisting of a polymer having a recurringunit of the structure expressed by the following formula (II-1)##STR10## (d-1) A polyoxyethylene nonylphenyl ether (the number ofpolyoxyethylene recurring units: 9).

INDUSTRIAL APPLICABILITY

It is clear from the tables 1 and 2 that the antistatic films of theexamples are excellent in all of antistaticity, back-transferresistance, reclaimability, chipping resistance and blocking resistance.

What is claimed is:
 1. An antistatic polyester film having an antistaticlayer formed of an antistatic agent (A) composed mainly of a polymerhaving a recurring unit of a structure expressed by the followingformula (I) on at least one surface of a polyester film ##STR11##wherein R¹ and R² are each H or CH₃, R³ is an alkylene group having acarbon number of 2 to 10, R⁴ and R⁵ are each a saturated hydrocarbongroup having a carbon number of 1 to 5, R⁶ is an alkylene group having acarbon number of 2 to 5, n is a number of 1 to 40, m is a number of 1 to40, Y⁻ is a halogen ion, a mono- or polyhalogenated alkyl ion, nitrateion, sulfate ion, an alkylsulfate ion, sulfonate ion or analkylsulfonate ion.
 2. The antistatic polyester film of claim 1 whereinthe polyester film is a polyethylene terephthalate film.
 3. Theantistatic polyester film of claim 1 wherein the polyester film is apolyethylene 2,6-naphthalate film.
 4. The antistatic polyester film ofclaim 1 wherein the ion Y⁻ in the formula (I) is an alkylsulfonate ionexpressed by R⁹ SO₃ ⁻ wherein R⁹ is a saturated hydrocarbon group havinga carbon number of 1 to
 5. 5. The antistatic polyester film of claim 1wherein the group R³ in the formula (I) is ethylene group.
 6. Theantistatic polyester film of claim 1 wherein the group R⁶ in the formula(I) is ethylene group.
 7. The antistatic polyester film of claim 1wherein said film is provided with an antistatic layer formed by theapplication of a coating liquid having a solid composition composed of 5to 100% by weight of the antistatic agent (A) and 0 to 95% by weight ofat least one kind of a binder resin selected from the group consistingof a polyester resin (B-1), an acrylic resin (B-2) and an acryl-modifiedpolyester resin (B-3).
 8. The antistatic polyester film of claim 7wherein said film is provided with an antistatic layer having a surfaceenergy of 37 to 73 dyne/cm and a water contact angle of 40 to 110 degreeand formed by coating a base film with a water-based coating liquid,drying the coating layer and drawing the coated film wherein saidcoating liquid has a solid composition composed of 10 to 80% by weightof the antistatic agent (A), 20 to 80% by weight of the binder resin (B)and 0 to 25% by weight of a surfactant (D) wherein said antistatic agent(A) consists of a polymer having a weight-average molecular weight of3,000 to 300,000 and contains a recurring unit having a structureexpressed by the formula (I) (wherein R¹ and R² are each hydrogen atomor methyl group, R³ is an alkylene group having a carbon number of 2 to10, R⁴ and R⁵ are each a saturated hydrocarbon group having a carbonnumber of 1 to 5, R⁶ is ethylene group, and Y⁻ is an alkylsulfonate ionexpressed by the formula R⁹ SO₃ ⁻ (R⁹ is a saturated hydrocarbon grouphaving a carbon number of 1 to 5, and said binder resin (B) is anacrylic resin (B-2) having a second order transition point of 20 to 100°C.
 9. The antistatic polyester film of claim 1 wherein said film isprovided with an antistatic layer formed by the application of a coatingliquid having a solid composition composed of 5 to 99% by weight of thean antistatic agent (A), 0 to 95% by weight of a binder resin (B), and 1to 15% by weight of a crosslinking agent (C) composed mainly of apolymer having a recurring unit of a structure expressed by thefollowing formula (II) ##STR12## in the formula (II), the groups R⁷ andR⁸ are each H or CH₃.
 10. The antistatic polyester film of claim 9wherein said film is provided with an antistatic layer having a surfaceenergy of 37 to 73 dyne/cm and a water contact angle of 40 to 110 degreeand formed by coating a base film with a water-based coating liquid,drying the coating layer and drawing the coated film wherein saidcoating liquid has a solid composition composed of 10 to 80% by weightof the antistatic agent (A), 19 to 80% by weight of the binder resin(B), 1 to 10% by weight of a crosslinking agent (C) and 0 to 25% byweight of a surfactant (D) wherein said antistatic agent (A) consists ofa polymer having a weight-average molecular weight of 3,000 to 300,000and contains a recurring unit having a structure expressed by theformula (I) (wherein R¹ and R² are each hydrogen atom or methyl group,R³ and R⁶ are each ethylene group, R⁴ and R⁵ are each a saturatedhydrocarbon group having a carbon number of 1 to 5, and Y⁻ is analkylsulfonate ion expressed by the formula R⁹ SO₃ ⁻ (R⁹ is a saturatedhydrocarbon group having a carbon number of 1 to 5, and said binderresin (B) is an acrylic resin (b-2) having a second order transitionpoint of 20 to 100° C.
 11. The antistatic polyester film of claims 1,wherein said polyester film is a white polyester film having a thicknessof 50 to 300 μm and a light transmittance of less than 60%.
 12. Theantistatic film laminate A produced by laminating a magnetic layer onone surface of the antistatic polyester film described in the claim 11.13. The antistatic film laminate B having an ultraviolet ink layer on asurface of the antistatic film laminate A described in the claim 12opposite to the surface laminated with the magnetic layer.
 14. Theantistatic polyester film of claim 1 wherein said polyester film is atransparent polyester film having a light transmittance of 60% or over.